Low cost, miniaturization, shortening of examination time, simplicity of operation, and so forth are required for human diagnostic equipment used in each household, simple diagnostic facility, and the like. A sensor IC (Integrated Circuit) formed on a semiconductor integrated circuit can satisfy these requirements.
For example, PTL 1 discloses an example of a sensor IC formed on a semiconductor integrated circuit. The sensor IC according to PTL 1 will be described with reference to FIGS. 9 to 11.
Part (a) of FIG. 9 is a schematic diagram illustrating the configuration of the sensor IC of PTL 1, and part (b) of FIG. 9 is a circuit diagram of the sensor IC of PTL 1.
As illustrated in part (a) of FIG. 9, the sensor IC of PTL 1 has a configuration where oscillators 110 and 120 are arranged in parallel on a semiconductor substrate 101. The oscillator 110 includes an inductor 111 and another circuit 112, and the oscillator 120 includes an inductor 121 and another circuit 122. The inductors 111 and 121 are formed of metal layers on the semiconductor substrate 101. As illustrated in part (b) of FIG. 9, the other circuits 121 and 122 include transistors and capacitors.
Part (a) of FIG. 10 is a schematic diagram illustrating a state in which magnetic particles and an examination object are brought into contact with one inductor of the sensor IC, and part (b) of FIG. 10 is a diagram illustrating a state in which a further examination object is brought into contact with the other conductor.
As illustrated in part. (a) of FIG. 10, when an examination object 114 is brought into contact with the semiconductor substrate 101 illustrated in part (a) of FIG. 9, the permeability changes as a result of fluctuation of magnetic particles 113 attached to the examination object 114, and the inductance of the inductors 111 and 121 is affected by that change in permeability. Accordingly, the oscillation frequencies of signals output by the oscillators 110 and 120 change, and a detector (not illustrated) detects the changes in oscillation frequency of the signals. The changes in oscillation frequency indicate fluctuations in the physical properties of the examination object 114.
For example, as illustrated in part of FIG. 10, the examination object 114 is selectively brought into contact with the oscillator 110 in order to use one of the oscillators 110 and 120, namely, the oscillator 110, as a sensor section. The examination object may not be brought into contact with the other oscillator 120 in order to use the oscillator 120 as a reference section, or, as Illustrated in part (b) of FIG. 10, an examination object 124 serving as a reference may be brought into contact with the oscillator 120. Accordingly, the physical properties of the examination object 114 are evaluated by checking the difference in oscillation frequency between the signals of the oscillators 110 and 120 using an enable signal or an /enable signal.
FIG. 11 is a cross-sectional view taken along line A-A′ of part of FIG. 10. As illustrated in FIG. 11, even when a metal layer 130 configuring the inductor 111 is formed on the top layer in the semiconductor substrate 101, because there is a protective film 115 formed of an insulator or the like between the surface of the semiconductor substrate 101 and the metal layer 130 (induct of 111), the examination object 114 never contacts the metal layer 130 on the top layer. The same applies to the inductor 121.
In addition, NPL 1 describes a circuit in which, in a sensor IC such as that described above, the oscillation frequency of an oscillator is se to a value within the range from 1.1 GHz to 3.3 GHz in which the fluctuation range of the oscillation frequency in accordance with a change in magnetic susceptibility of magnetic particles is great.